1. Field of the Invention
The present invention relates to a device mounting board and a method of manufacturing the board, a semiconductor module and a mobile device.
2. Description of the Related Art
Recently, with the trend toward miniaturization and high performance of electronic devices, there is a demand for further reduction in the size of semiconductor devices used in electronic devices. With such miniaturization of semiconductor devices, it is of absolute necessity that the pitch between electrodes to enable mounting on a wiring board be made narrower. A known method of surface-mounting a semiconductor device is flip-chip mounting in which solder balls are formed on electrodes of the semiconductor device and the solder balls are soldered to an electrode pad of the wiring board. With this flip-chip method, however, there are restrictive factors for the narrowing of the pitch between electrodes, such as the size of the solder ball itself and the bridge formation at soldering. As one structure used to overcome these limitations, known is a structure where a bump structure formed on a substrate (wiring layer) is used as an electrode or a via, and the electrodes of the semiconductor device are connected to the bump structure by mounting the semiconductor device on the substrate with an insulating resin layer, such as epoxy resin, held between the semiconductor device and the substrate.
However, in the aforementioned structure in which the bump structures formed on the substrate and the electrodes of the semiconductor device are connected together, there is a fear that heat stress generated due to a difference between the coefficients of thermal expansion of the substrate and the semiconductor device, may be concentrated into a connection portion between the bump structure and the substrate. In particular, when stresses in the Z direction (direction in which the bump electrode is peeled off from the silicon substrate (semiconductor device)) are concentrated into the connection portion between the bump electrode and the wiring layer, there is a fear that the connection reliability between the bump electrode and the semiconductor device may be deteriorated.